The present invention relates to a vehicle tire. Specifically, the invention relates to a pneumatic vehicle tire having an improved tread portion that reduces the formation of anomalies causing subjective user dissatisfaction.
Tires, especially commercial vehicle tires sometimes have to be removed from service due to anomalies on the tread region and particularly the shoulder tread region. These anomalies are depressions in the tread rib or tread blocks forming the rib. The anomalies are generally caused by unequal radial stress distribution laterally across the rib or blocks. The highest stress concentration occurs at the outer edges of the rib or blocks. This high stress concentration at the edges and particularly the outer edges of the rib or blocks is known as the edge effect. The central portion of the rib or blocks experiences lower stress than the edges. As a result, the anomalies typically begin to form at the edges of the rib or blocks.
Once an anomaly forms at the edge of the rib or blocks, the anomaly will propagate to the remainder of the rib or blocks; and often to adjacent ribs or blocks. The propagation of the anomaly occurs quickly as the tire continues to roll.
The decision to remove a tire is subjective and may depend on the location of the tire on the truck/trailer combination. Generally, a driver can feel an anomaly on a steering tire by the ride of the vehicle. In that case, the driver pulls the tire when uncomfortable with the ride of the vehicle. However, if a tire having an anomaly is a drive tire or is located on the trailer, the driver may not sense any discomfort. The driver may, however, hear an increase in tire noise. If the driver does not sense discomfort or an increase in noise, the driver will pull the tire during a subsequent visual inspection of the vehicle.
The removal of a tire due to anomalies causing subjective user dissatisfaction is premature when considering the portions of the tire without the anomaly. The portions of the tire without the anomaly are capable of substantial additional service on the vehicle. Extending the time until the onset of an anomaly or decreasing the severity of the anomaly once found may extend the life of the tire. The extended life of the tire reduces the cost of purchase and installation of new tires. In the commercial trucking field, these potential cost savings are significant.
Accordingly it is an object of the present invention to provide an improved tread portion that reduces the formation of anomalies causing subjective user dissatisfaction.
It is a further object of the present invention to reduce or eliminate the high normal stress distribution at the lateral edges of a tread rib or blocks.
It is a further object of the present invention to more uniformly distribute the normal stress laterally across the tread rib or blocks.
It is a further object of the present invention to reduce the radial stiffness at a lateral edge of a tread rib or blocks.
It is a further object of the present invention to maintain the lateral rigidity of a tread rib or blocks while reducing the radial stiffness at the edge of the rib or blocks.
It is a further object of the invention to provide sequential radial and lateral support for the shoulder ribs or blocks.
It is a further object of the invention to provide an improved shoulder construction of the tread portion of a tire.
It is a further object of the invention to provide conforming image support structure for the shoulder ribs and blocks
It is a further object of the present invention to provide a tread rib or block capable of resisting tearing or cracking during.